1. Field of the Invention
This invention relates to an operating device, such as an operating pedal device for a vehicle, and more particularly, to an improvement in the operating device with a load sensor electrically detecting an operating force.
2. Description of the Related Art
A following device is known as an operating device provided with or equipped with a load sensor. This operating device with load sensor includes (a) an operating member operated to be moved, (b) a reaction force member to which an operating force of the operating member is transmitted, to which a reaction force corresponding to the operating force is acted, (c) at least one pivotal movement connecting portion that is disposed between the operating member and the reaction force member, to connect a pair of members to be relatively pivotable around a connecting pin, and to transmit an operating force through the connecting pin, and (d) a load sensor electrically detecting an operating force.
A brake pedal device for a vehicle disclosed in a following Patent Document 1 is an example of such the operating device with a load sensor. A push rod (i.e., a reaction force member) protruding from a master cylinder is connected to a connecting pin projected on a side portion of an operating pedal to be relatively movable in an axial direction. A displacing amount of the push rod displacing relative to the connecting pin resisting the urging force of a spring is detected by a sensor.    Patent Document 1: U.S. Pat. No. 5,563,355
However, in the device disclosed by Patent Document 1, because the push rod is required to have a slotted opening for the relatively movable connection, a general push rod cannot be used for this device without being changed. Additionally, in accordance with the depressing operation of the operating pedal, the push rod pivots relative to the connecting pin. Therefore, a spring that biases or urges the push rod and a sensor that detects the displaced amount are also required to be arranged to pivot relative to the connecting pin, thus making the structure of the device complex. Still additionally, because the push rod, the spring and the sensor are disposed beside the operating pedal, especially a brake pedal is required to have a sturdy structure to secure a stable operating state, thus resulting in increase in both size and cost as a whole.
In contrast, a technique, though not yet well known, for compactly arranging a load sensor at a connecting position of a clevis pin has been proposed as shown in FIG. 25. FIGS. 25A and 25B show an operating pedal device 200 used in a service brake for a vehicle, of which FIG. 25A is a front view thereof, and FIG. 25B is an enlarged view along line XXVA-XXVA of FIG. 25A. A pedal support 12 fixed integrally to a vehicle body has a plate-like operating pedal 16 disposed pivotably around the axis of a substantially horizontal support shaft 14. The operating pedal 16 is depressed with the foot of a driver in accordance with braking instructions. A pad 18 is disposed at a lower end of the operating pedal 16, and an operating rod 22 of a brake booster is connected to a middle portion of the operating pedal 16 by a pivotal movement connecting portion 20.
The pivotal movement connecting portion 20 is composed of a U-shaped clevis 24 fixed integrally to an end of the operating rod 22 by a screw for example, and a clevis pin 26 disposed on the operating pedal 16 to be parallel to the support shaft 14. The operating rod 22 and the operating pedal 16 are connected to be relatively pivotable around the axis of the clevis pin 26. The clevis pin 26, corresponding to a claimed connecting pin, has axial ends projecting sideways from the operating pedal 16, and is held not to slip off from the U-shaped clevis 24 by a snap ring or a retaining pin.
An output corresponding to the operating force of the operating pedal 16 is transmitted to the operating rod 22 through the pivotal movement connecting portion 20, and a reaction force corresponding to the output is acted i.e., allowed to act by a brake booster. The operating rod 22 corresponds to a claimed reaction force member. If the operating pedal device is of a by-wire type which electrically controls a wheel brake, a reaction force member in which a predetermined reaction force is acted by a reaction force mechanism for example, is connected instead of the operating rod 22.
The operating pedal 16 has a sensor attaching hole 202 greater in diameter than the clevis pin 26 at a connecting position with the clevis pin 26. A load sensor 30 is disposed in an annular space formed between the sensor attaching hole 202 and the clevis pin 26. The load sensor 30 is composed of a cylindrical deforming member 32, an annular member 34 disposed radially outside, i.e., on an outer periphery surface of the deforming member 32, and a shaft-like member 36 disposed radially inside of, i.e., on an inner periphery surface of the deforming member 32. The load sensor 30 is used to detect a load applied to the deforming member 32 in the radial direction thereof. The annular member 34, corresponding to a claimed main body member, is integrally attached to a sensor attaching hole 202 with a predetermined posture (phase) by a press fitting or by use of a bolt or a leaf spring, and integrally holds one axial end (i.e., an upper end in FIG. 25B) of the deforming member 32 by welding for example.
The shaft-like member 36 integrally holds other axial end (i.e., a lower end in FIG. 25B) of the deforming member 32 by welding for example, and has a through-hole 38 formed in an axis part through which the clevis pin 26 passes. The clevis pin 26, the through-hole 38 and the clevis 24 are constructed to be relatively rotatable, so that the member having less friction is relatively pivoted in accordance with the depressing operation of the operating pedal 16. However, to reduce friction, bearings or the like may be disposed therebetween, if necessary.
Thus, the annular member 34 and the shaft-like member 36 are mutually connected through the deforming member 32. If the load is externally applied in the radial direction, i.e., in the direction perpendicular to the axis is nearly zero, the members 32, 34 and 36 are held to be substantially concentric, i.e., coaxially with the axis of the clevis pin 26. On the other hand, if the load is radially applied between the annular member 34 and the shaft-like member 36 by the reaction force of the operating rod 22 in accordance with the depressing operation of the operating pedal 16, the deforming member 32 undergoes a shear strain. As a result, the annular member 34 fitted to the operating pedal 16 displaces in a direction approaching the operating rod 22 (i.e., leftward in FIG. 25) relatively with respect to the shaft-like member 36.
An annular space is provided between the annular member 34 and the shaft-like member 36 to allow the annular member 34 and the shaft-like member 36 to radially displace relative to each other, or to allow the deforming member 32 to undergo the shear strain. The deforming member 32 made of a metallic material such as ferritic stainless steel, can be elastically deformed by receiving a radial load, and it undergoes the shear strain in accordance with the operating force generated by depressing the operating pedal 16.
To detect the shear strain of the deforming member 32, strain detecting elements such as strain resistive elements are attached to an outer or inner circumferential surface of the deforming member 32, and they are connected to a control circuit section of a vehicle through a wire harness 56. The operating force of the depressing operation can be detected based on an electric signal output from the strain detecting elements.
In the vehicular operating pedal device 200 thus constructed, in the pivotal movement connecting portion 20 which transmits an operating force applied onto the operating pedal 16 to the operating rod 22, a sensor attaching hole 202 is formed on the operating pedal 16 pivotably connected relative to the operating rod 22 via the clevis pin 26. The hollow cylindrical load sensor 30 is disposed in an annular space formed between the sensor attaching hole 202 and the clevis pin 26. Therefore, with the rotating moment such as twist which may be applied to the load detecting element 30 suppressed, the whole of the operating pedal device 200 can be formed in simple and compact structure. Additionally, relating members such as the operating rod 22 and the clevis 24 which are the same as those used in the conventional pedal device can be used, so that the operating pedal device 200 can be produced at low cost.
However, even in the thus structured operating pedal device 200, when the operating pedal 16 is pivoted around the supporting shaft 14 in accordance with the depressing operation thereof, the operating rod 22 and the operating pedal 16 are also relatively pivoted around the axis of the clevis pin 26. As a result, an acting position of the load applied to the deforming member 32, i.e., a deforming direction of the deforming member 32 varies, so that a detected value may be varied in response to variation in the load acting position. Size and a setting position of the strain detecting element are determined to detect such deformation, regardless of variation i.e., shift of the varying position of the deforming member 32. However, due to continuous movement of the detecting position in the circumferential direction, there is a problem that the deforming form of the deforming member 32 is complex and easily varies. For this reason, securing a high detecting accuracy may be difficult depending on the relative positional relationship between the operating rod 22 and the operating pedal 16.
The present invention has been made in consideration of these circumstances. Therefore, an object of the present invention is, in an operating device that has a load sensor disposed in a pivotal movement connecting portion and that is capable of detecting an operating force transmitted via a connecting pin, to improve the detecting accuracy of the load sensor. In the operating device, a shaft-like member and a main body member (i.e., an annular member 34 of FIG. 25B) are relatively changed in the position to each other in the direction perpendicular to the axis of the shaft-like member, and the load sensor electrically detects an operating force based on this change.